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backflow preventer concerns

I am preparing to winterize my daughter's sprinkler system. It has been done by a professional in the past and she lives near Kansas City. The backflow preventer is mounted a foot below grade in a valve box, 3' from the main water meter in the front yard, and there is a valve between the meter and the BFP in the box. The BFP is mounted horizontally and is half covered in mud/dirt. It has not been removed in the winter. It has 4 test cocks that stand vertically and neither end of the BFP has a valve shutoff. The upstream riser to the BFP is buried and not accessible and it appears there is no riser on the downstream end.

I plan to shut off the main valve and blow 50# of air through the most-upstream test cock of the BFP just long enough to clear the water out of it. Then I'll use the most downstream test cock to blow out the full system. There is no other port available other than the test cocks of the BFP. I am pretty sure that is how it has been done in the past, but I'm not positive. The seven zone valves are in the backyard.

Should I be concerned that the BFP is allowed to remain outside and pretty much unprotected from the cold weather during the winter?

Am I overlooking any critical considerations?

You kind folks helped me install my sprinkler system three years ago and it has worked fine now for three seasons.

Thank you for your time.

Frank

This post has been edited 1 times, last edit by "Frankpc" (Nov 1st 2011, 12:27pm)

I should have been more clear. The sprinkler system I am about to winterize is my daughter's system. The system you and others helped me with was my system. I have winterized my system three times now without incident.

But I have not yet worked on my daughter's system. This will be the first time and I am looking for guidance in the areas I outlined.

I cleaned some of the mud off of the backflow preventer. I now know it is a Watts and the model number is something like: 007M3DC (QT?) 3/4" double check valve I believe. Perhaps you can tell more from the picture. It has the threaded shafts for the valve handles. But I wouldn't want to try to turn them. The downstream end is on the left. I am hoping I can loosen the test cock set screw on that end. I don't know whether I should try to loosen the set screw on the right to be able to blow air through it. I will spray some Liquid Wrench on them first.

This post has been edited 1 times, last edit by "Frankpc" (Oct 31st 2011, 3:25pm)

If those testcocks are the only place you can connect your air, then you need to get a 1/4-inch "female flare" adapter to get to a pipe thread. Don't do anything to the testcocks, unless no other option exists (and they do exist) - those flare-end testcocks are to connect to the hoses of a backfow tester.

That looks like a mess waiting to happen! I would first scour the area for a seperate blow out point. Only after I was 120% convinced I had to connect to a test cock, would I attempt it. I would first submit a bid to move the RPZ to a more reasonable location.

I'll look for a 1/4" female flare adapter today at Lowes. I think the threads look pretty good and the top flared surface looks smooth.

I can't find any other blow out point. But her sod is in really good shape and it could have easily grown over a smaller access box - especially the 6" round type. I found one box that contains 4 valves and I had to cut away a lot of sod to get the lid off. Since there are seven zones, there are 3 valves that I haven't found, so I expect a blow out point could be hidden as well. I have confirmed that the person who used to blow out the system used the testcock port.

I've been considering feeding an audio or radio frequency signal into the wires at the control panel. Then, perhaps, I will be able to trace the signal to find the valves. But it would seem that won't help to find a blow out point.

I agree that the backflow preventer is in bad shape and should have been taken care of.

update

I used a metal detector and found a zone valve in a 6" cylindrical box. 2 missing valves to go. I was actually looking for a buried port to use for blow out. No luck there.

I bought two brass fittings and a 2' piece of 1/4" copper tubing to connect them together. One is a 1/4" female flare to 1/4" compression. And the other is a 1/4" female NPT to 1/4" compression. that seemed to be the best I could do. I am sure there is a less complicated way to connect the backflow preventer test cock to an pneumatic fitting. But I couldn't find it at Lowes or Home Depot.

Sure seems like the passageway through all of that stuff will restrict the airflow. I am hoping the copper doesn't melt.